On-line measurement of this type is used, for example, in the data system of the USTER SLIVERDATA (USTER is a registered trademark of Zellweger Uster AG) which is employed to monitor quality and production in the preparatory apparatus of a spinning mill. Within the scope of quality monitoring, the silver count and periodic and virtually periodic mass fluctuations are checked, in addition to mass non-uniformity.
It is known that most faults influencing the quality of the final product are caused by fluctuations in the silver count, silver non-uniformity, periodic mass fluctuations and drafting faults. In addition to this certain knowledge, it may be assumed that, on the basis of practical experience, short thick places also cause duality problems. This is because thick places of such a kind lead to cost-intensive disruptions in production and, moreover, influence the quality of the final product and the efficiency of all of the process steps.
It has hitherto been possible to detect short thick places only by laboratory tests. These short thick places arise as a result of sliver accumulations, defective machine parts, inadequate maintenance and cleaning and incorrect machine settings, and can occur very frequently. Bearing in mind that 50 bobbins of yarn or more can be manufactured from the quantity of sliver produced in only one minute on a modern high-performance drafting frame, it becomes clear that the laboratory test cannot prevent serious losses of quality. Such a goal is possible only by way of on-line monitoring.